Ultra-thin interfacial domain wall less than 1 nm based on TbxCo100−x/Cu/[Co/Pt]2 heterostructures for multi-level magnetic pillar memory

Abstract

We propose a new pillar type of multi-level memory with TbxCo100−x/Cu/[Co/Pt]2 heterostructures to achieve high storage density and controllable domain wall position in-memory applications. The structure consists of amorphous ferrimagnetic Tb–Co alloy films and ferromagnetic Co/Pt multilayers separated by less than one monolayer of Cu. Here, we observe that the interfacial domain wall energy density can be controlled by changing the interlayer thickness of Cu and Tb–Co composition. We also observe two competing mechanisms, one leading to an increase and the other to a decrease, corresponding to the effect of Tb content on saturation magnetization and coercivity of heterostructures. Theoretical and experimental results show that by tuning the Tb–Co composition, we were able to decrease domain wall (DW) width and precisely control the DW position of the multilayer structure. The interfacial domain wall width is significantly decreased to less than 1 nm compared to other reports. Moreover, controlling the DW position and width offers a novel multi-level magnetic memory with high performance compared to conventional memory applications.